The FBI director just gave a striking example of how much of a problem encryption has become

Encrypted communications are increasingly thwarting intelligence agencies that are working to detect terrorist activity.

And a comment Wednesday from the FBI’s director emphasises how serious the issue has become.

At a Senate Judiciary Committee hearing on Wednesday, FBI Director James Comey said encryption is a “big problem” that the US must grapple with, especially in light of recent ISIS-linked terror attacks that have hit Europe and the US.

“In May, when two terrorists attempted to kill a whole bunch of people in Garland, Texas, and were stopped by great local law enforcement … that morning before one of those terrorists went to attempt mass murder, he exchanged 109 messages with an overseas terrorist,” Comey said.

“We have no idea what he said because those messages were encrypted. And to this day I can’t tell you what those messages said with that terrorist 109 times the morning of that attack. That’s a big problem, and we have to grapple with it.”

ISIS (also known as the Islamic State and ISIL) claimed responsibility for the Garland attack. Two gunmen, who authorities have said inspired by ISIS rather than directly tied to the group’s core base in the Middle East, opened fire at a contest that featured drawings of the Prophet Muhammad. The gunmen, who started shooting outside the venue where the contest was held, wounded a security guard before other officers shot and killed them.

One of the shooters was reportedly known to the FBI long before the Garland attack. For weeks before the shooting, ISIS supporters on the internet had been calling for attacks on the drawing contest.

It’s not just Garland, either — the issue of encryption came up again after terrorists affiliated with ISIS carried out attacks across Paris in November, killing 130 people and wounding hundreds more.

Authorities haven’t confirmed whether the attackers used encrypted communications to coordinate the attack, but ISIS sent out a claim of responsibility first on Telegram, an app known for its high level of encryption. ISIS-affiliated extremists use the app for disseminating propaganda as well as communicating privately.

“Terrorists are using encrypted communications and … very solid cryptography standards that haven’t been broken yet,” said David Kennedy, the CEO of TrustedSec who has worked with the Marine Corps’ cyber-warfare unit and the National Security Agency, in November.

He added: “The terrorists are getting very smart on their mode of communications.”

Government officials have also expressed similar thoughts. CIA Director John Brennan told an audience at the Center for Strategic and International Studies in November that terrorists “have gone to school on what they need to do in order to keep their activities concealed from the authorities.”

“I do think this is a time for particularly Europe as well as the US for us to take a look and see whether or not there have been some inadvertent or intentional gaps that have been created in the ability of intelligence services to protect the people that they are asked to serve,” Brennan said.

“Among the most popular are WhatsApp, Kik, Surespot, and Telegram,” Berger wrote. “… The shift to such applications has been described by FBI Director James Comey as ‘going dark’ — the point at which continued monitoring by law enforcement becomes problematic.”